AlN Lamb Wave Delay Line Structure for High-Q 10 GHz Operation
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Solution Overview
Problem
Current acoustic wave elements in radio frequency systems face challenges in achieving high frequency operation while maintaining a high quality factor (Q) and large effective electromechanical coupling coefficient (k2), particularly in generating lowest-order antisymmetric mode Lamb waves for applications such as delay lines and filters.
Innovation Solution
The acoustic wave element incorporates a piezoelectric layer of aluminum nitride (AlN) with a diamond-like carbon (DLC) layer and a support layer, along with interdigital transducer electrodes, to generate Lamb waves with specific thickness and material configurations that enhance acoustic velocity and mechanical ruggedness, allowing for high frequency operation and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acoustic wave elements are used for high frequency operation, then frequency increases, but quality factor (Q) and electromechanical coupling coefficient (k2) deteriorate
Solution Approach 1:
The patent employs a composite structure consisting of a piezoelectric layer (such as aluminum nitride or zinc oxide) deposited on a diamond-like carbon (DLC) layer, which itself is on a substrate. This composite material architecture enables high frequency operation (up to 10 GHz and above) while maintaining high quality factor and electromechanical coupling coefficient by combining the piezoelectric properties of the first layer with the mechanical ruggedness and acoustic velocity characteristics of the DLC layer.
2Reliability
If piezoelectric layer thickness is increased to improve coupling coefficient, then electromechanical coupling coefficient (k2) improves, but acoustic velocity and frequency operation deteriorate
Solution Approach 1:
The patent optimizes the thickness of the piezoelectric layer to a specific range (0.1λ to 1λ, where λ is the wavelength) to achieve the desired balance between electromechanical coupling coefficient and acoustic velocity. By precisely controlling this parameter within the specified range, the device attains both high coupling efficiency and high frequency operation capability.
Solution Approach 2:
The invention introduces a diamond-like carbon layer with specific properties (high acoustic velocity, mechanical ruggedness) beneath the piezoelectric layer. This creates local quality differentiation where the DLC layer provides the mechanical foundation for high acoustic velocity while the piezoelectric layer above it provides the electromechanical coupling, allowing both parameters to be optimized independently.
3Strength
If conventional materials are used to improve mechanical ruggedness, then structural strength improves, but acoustic velocity and frequency performance deteriorate
Solution Approach 1:
The patent utilizes diamond-like carbon (DLC) material for the support layer, which combines exceptional mechanical ruggedness with very high acoustic velocity. This composite approach allows the device to achieve both improved structural strength and enhanced acoustic performance, enabling high frequency operation while maintaining mechanical durability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables high frequency operation up to 10 GHz with maintained quality factor (Q) and effective electromechanical coupling coefficient (k2), providing improved structural ruggedness and low-loss performance for acoustic wave elements in radio frequency applications.
Implementation Method 1
An acoustic wave filter can include a plurality of resonators arranged to filter a radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, and Lamb wave filters.
Data Source
AI summary
An acoustic wave element is disclosed. The acoustic wave element can include a piezoelectric layer that includes aluminum nitride. The acoustic wave element can also include a diamond like carbon layer. The acoustic wave element can further include an interdigital transducer electrode that is positioned on the piezoelectric layer. The piezoelectric layer is positioned between the interdigital transducer electrode and the diamond like carbon layer. The acoustic wave element is configured to generate a Lamb wave having a wavelength of λ.